CD27+ B cells in human lymphatic organs: re-evaluating the splenic marginal zone

Area of Science:

• Immunology
• Cell Biology
• Anatomy

Background:

• The marginal zone of human spleens has been considered a unique site for sessile memory B cells, based on rodent studies.
• This understanding is challenged by new findings on B cell distribution in human lymphoid tissues.

Purpose of the Study:

• To investigate the distribution and characteristics of CD27(+) B cells in human secondary lymphatic organs.
• To compare human splenic microanatomy with that of rodents.
• To propose a new hypothesis regarding B cell recirculation in humans.

Main Methods:

• In situ detection of CD27(+) B cells in human spleen, lymph nodes, appendix, tonsils, and terminal ilea.
• Analysis of B cell populations based on CD27 and Immunoglobulin D (IgD) expression.
• Comparative microanatomical analysis of human and rodent splenic white pulp.

Main Results:

• CD27(+) B cells are found in the superficial regions of B cell follicles in various human lymphoid organs, not exclusively in the spleen's marginal zone.
• A distinct microanatomical organization of the human splenic white pulp compared to rodents was identified.
• The follicular periphery in human secondary lymphatic organs appears to be a recirculation compartment for both naive and memory/natural reactive B cells.

Conclusions:

• The distribution of CD27(+) B cells suggests a fundamental difference between human and rodent splenic white pulp microanatomy.
• The follicular periphery in human secondary lymphatic organs may serve as a shared recirculation site for naive and memory B cells.
• Human and rodent B memory cells likely exhibit different recirculation behaviors.